Air

Air is the mixture of gasses in the earth's atmosphere. A straw can be used to suck the air out of a bag.

It is also an important ingredient in whipped applications, like whipped cream, omelets... you do like a fluffy omelet, don't you?... and, when altitude; that is, atmospheric pressure, is an issue, becomes a factor in cooking times of all sorts of scientific-like equations... like how long it takes for water to boil.